Morphmetric Analysis of Randenigala Reservoir Catchment using GIS

Abstract

Morphometric techniques play a major role in addressing the quantitative description of the geometry of the drainage basins and its network. This helps in characterizing the drainage network, comparing the characteristics and examining the effect of lithology, rock structure and rainfall. The study focuses on analysis of morphometric features of Randenigala reservoir catchment based on available digital data using GIS. River Mahaweli was dammed closer to MinepeAnicut to build Randenigala reservoir with the elevation of 160 m to 240 m (7 8 to 7 14N and 80 48 to 80 49 E). The capacity is 861 MCM and catchment comprise of 448 km2 in the Kandy and Nuwara-Eliya districts. The elevation of the catchment ranges from 240 m to 2500 m. Method of Horton and Strahler (1945) was used to rank the stream segments. The stream numbers were entered into the table and other analyses based on the mathematical formulas. The results indicated that the catchment area was 448.9 km2, perimeter 111.24 km, mean slope 36.8, axial length 30.5 km, basin width 14.72 km, form factor 0.48, compactness factor 1.48, circulatory ratio 0.46, elongation ratio 0.78, orders of stream network indicated, 1315 of first orders, 314 of 2nd, 72 of 3rd, 15 of 4th, 3 of 5th, 1 of 6th and one seventh order stream. The stream frequency and drainage density were 3.83 (no. of streams /km2) and 2.43 (km/km2). Bifurcation ratio was 3.65 and length of overland flow was 0.21 km. These findings are useful in determining the effect of catchment characteristics such as size, shape, slope of the catchment and distribution of stream network.